The purpose of this study is to determine accuracy of a method that assesses muscle protein breakdown and formation which uses samples of arterial (blood going to tissues) and venous (blood coming back from tissues) blood samples compared with the method of measuring protein breakdown and formation which involves direct sampling of muscle protein (the traditional method). Protein formation can be determined by giving intravenous naturally occuring non-radioactive labeled amino acids (protein building blocks) and performing needle muscle bioopsies with blood sampling. These samples are then studied to determine rates of protein formation and breakdown. The new method we are studying will not require muscle biopsy if it is proved to be accurate. This would make future studies much easier to perform. This study will also involve infusing insulin, a naturally occuring human hormone, into the leg to verify its effects on muscle protein handling. The study is closed to participants currently. All studies are complete. Analysis of the samples is being completed. Dr. Claudio Cobelli, co-investigator in the study, is developing a mathematical model from the results of the study.